The invention relates to a process, and related apparatus, for external measurement and analysis of uterine contractions, particularly for early indications of impending premature birth.
Reducing the mortality rate of new-born infants is a significant obstetric problem. In this respect, it has been observed that the great majority of early infant deaths is the result of premature birth, with the infants being born in premature condition, with low body weight. In many cases, even with extraordinary dedication of personnel and resources, it is not possible to save many prematurely born infants. For this reason, significant efforts have been focused on preventing such premature births.
It is well known that contractions of the uterus can be detected to occur throughout the whole time of a pregnancy. As described in detail by M. Katz, P. J. Gill and R. B. Newman in the American Journal of Obstetrics and Gynecology, 1986, Issue No. 154, significant differences can be detected in the intensity and frequency of uterine contractions between groups of pregnant women giving normal birth in due course and those whose pregnancies end in premature birth. The frequency and intensity of uterine retractions throughout much of the period of pregnancy in the latter group of women are considerably higher than in the case of women who give birth in the normal course. It is also well established that the activity of the uterus several days prior to birth becomes significantly stronger, giving an early warning of the probable start of the birth. If detected in time, these early warning indications can be responded to, to ward off otherwise premature birth.
A well known means for the measurement of uterine contraction activity utilizes a pressure sensing device which is strapped on to the abdominal wall of the pregnant woman. Uterine contraction activity is detected by a pressure sensing transducer, which generates an electrical signal capable of being evaluated by a gynecological specialist. Principally, these apparatuses are somewhat large and cumbersome, and are available only for clinical use under medical supervision. Necessarily, the observation time is relatively short, and the facilities is not available to large numbers of expectant mothers.
An improvement in the above system is described by M. Katz and P. J. Gill in the American Journal of Obstetrics and Gynecology, 1986, Issue No. 66. The described instrument is portable and can be used in the home of the patient. It consists of a traditional pressure sensing unit which is arranged to record uterine activity over a period of about 200 minutes. The data sensed during the observation interval is stored, and then transmitted via modem and telephone to the medical specialist. If necessary, the patient is advised to come in for observation. A major disadvantage of this arrangement is that it requires a rather highly developed infrastructure, an efficiently functioning telephone network, and permanent 24 hour monitoring by the medical facility. Although the instrument is portable, its size is relatively large, and the modem/transmitter arrangement and the evaluating receiver are required parts of the system, making it somewhat complicated and costly.
The present invention is directed to a new procedure, and to related apparatus, which may be made available on a large scale basis for home use by pregnant women for the monitoring of uterine contraction activity. The procedure of the invention is based upon the recognition that effective monitoring, for early detection of possible premature birth, requires a relatively high degree of continuity in the monitoring. Further, in order to provide a high degree of universality and acceptability, the procedure must be relatively simple, comfortable, economical and effective.
The procedure and apparatus of the invention take advantage of our observation that impending premature birth can be recognized by the occurrence of uterine contractions of an intensity level and duration in excess of a predetermined threshold, occurring at a frequency greater than a predetermined number per unit of time. Accordingly, the procedure of the invention does not have to rely upon a continuous measurement and storage of the data to frequency and intensity of uterine contractions. Rather, it ignores those contractions of a lower than threshold intensity, and of shorter duration than a predetermined time. With respect to those contractions whose intensity and duration exceed the threshold limits, the procedure of the invention makes no effort to record for later evaluation either the intensity or the duration of such contractions, but rather simply in effect indexes a counter registering the fact that such a contraction did occur, and records the time of its occurrence.
Pursuant to the procedure of the invention, vast amounts of significant information are distilled to a few items of data, which is stored for evaluation. The data stored is simply the number of contractions exceeding the threshold values and the times when such contractions occurred. If the number of registered contractions in a given period of time, for example, in excess of four or five per hour, an audible alarm can be sounded, so that the patient knows to get in touch with her medical adviser. Where desired, the stored data can be downloaded into the medical adviser's system for more detailed analysis.
Because the procedure of the invention requires the storage of only a minimum amount of data, it is possible for a simple, low cost home device, utilizing simple IC chips, to enable extended monitoring of the patient. This provides for a greatly increased degree of probability that an impending premature birth may be detected in time to be avoided by proper medication and treatment. For example, even a simple device according to the invention, and utilizing the above described procedure, can be used to measure uterine contractions continuously for a period of at least 24 hours. At the end of such period, the data can be downloaded, if desired, or the device can simply be reset for a subsequent period of monitoring. Depending upon the anticipated likelihood of premature birth with a given expectant mother, the device may be used on a periodic basis, within the same total limits of its data storage capacity. For example, rather than continuous monitoring for 24 hours, the device may be used in daily three hour periods over a span of eight days, or, for example, in daily one hour periods over a span of 24 days. When the device is used in the periodic manner, continuous monitoring may obviously be initiated at any time that the periodically monitored data indicated a potential problem.
For a more complete understanding of the above and other features and advantages of the invention, reference should be made to the following detailed description of preferred embodiments of the invention and to the accompanying drawing.